1. Field of the Invention
The present invention relates to a shroud for an axial flow fan wherein the shroud surrounds the axial flow fan and fixes and supports the axial flow fan and an axial flow fan driving motor and more particularly, to a shroud for an axial flow fan, which can guide a part of air blown by the axial flow fan in a direction in which parts requiring cooling are installed.
2. Background Art
An axial flow fan is a fluid machine for axially blowing air by rotating a plurality of blades radially arranged. In general, the axial flow fan constitutes an axial flow fan shroud assembly together with a shroud for axially guiding air whiling surrounding the axial flow fan.
The axial flow fan shroud assembly for an automobile is used to promote heat radiation of an air-cooled type heat exchanger, such as a radiator or a condenser, and blows air to the heat exchanger. The axial flow fan shroud assembly is classified into a pusher type and a puller type according to an arrangement form of the heat exchanger.
The pusher type axial flow fan shroud assembly adopts a method that the axial flow fan forcedly blows air from the front of the heat exchanger toward the back. Such a pusher type axial flow fan shroud assembly is used in a case that a space formed at the back of the heat exchanger inside an engine compartment is small since it provides a low air-blowing efficiency to the heat exchanger. Meanwhile, the puller type axial flow fan shroud assembly adopts a method that the axial flow fan located at the back of the heat exchanger sucks the forward air of the heat exchanger thereby to pass the air through the heat exchanger. The puller type is applied to most of automobiles since it provides higher air-blowing efficiency than the pusher type.
In the axial flow fan shroud assembly, as shown in FIGS. 1 and 2, the shroud fixes and supports the axial flow fan 2 on the rear side of the heat exchanger 20 and axially guides air sucked by the axial flow fan 2 in front of the heat exchanger. As shown in FIGS. 1 and 2, the shroud generally includes: a housing 10, a plurality of arms 11 centripetally extending from the inner peripheral surface of a ventilation hole 10a formed in the housing 10; and a motor fixing part 12 supported by the arms 11 for fixing and supporting an axial flow fan driving motor 3.
The housing 10 is in the form of an approximately rectangle corresponding to the heat exchanger 20, so that the front surface of the housing 10 is in contact with the entire rear surface of the heat exchanger 20 to enlarge a blowing area against the heat exchanger 20. The housing 10 has brackets formed integrally to the top and bottom thereof to be fixed on the heat exchanger 20. The ventilation hole 10a formed at the center of the housing 10 is in a circular form of a size large enough to surround the axial flow fan 2 as some interval to enhance blowing efficiency by reducing a loss of wind pressure of the axial flow fan 2.
Meanwhile, a function of the prior art axial flow fan shroud adopted to the automobile is restricted to transfer negative pressure by air blast of the axial flow fan 2 to the entire heat exchanger 20 while fixing the axial flow fan 2 and the driving motor 3. However, on the rear side of the shroud, components weak to heat, such as an alternator 35 are mounted. The alternator 35 is a device to generate electricity using a rotation of the engine during traveling of the automobile. Electricity generated by the alternator 35 charges a battery, and then used to operate electric machines of the automobile. The alternator 35 must not to be exposed to heat and needs to rapidly emit heat generated during an electricity generating process since it is equipped with parts made of insulating material weak to heat for heat-insulation between the parts to generate electricity.
If the parts weak to heat are displaced from an axial direction of the shroud ventilation hole 10a and deflectively mounted to one side due to a special restriction, or if they are mounted beneath the motor 3, cool air cannot be blown to the part, and axially blown air is dispersed into the engine compartment in a heated state after being pumped to a high-temperature engine 30, whereby it may have a fatal influence on performance and lifespan of the parts weak to heat.
That is, as shown in FIG. 3, since the engine 30 is located at the lower part of the rear side of the axial flow fan shroud assembly, air blown axially by the axial flow fan 2 is pumped to the engine 30 located at the back of the axial flow fan 2 to stop a smooth flow of air. Thereby, blown air is dispersed into the engine compartment in the heated state by the engine 30, so that all parts mounted inside the engine compartment are influenced by heat that may cause a fatal influence on the performance and lifespan of the parts weak to heat.
Therefore, in the case where the parts sensitive to heat are arranged at locations displaced from the axial direction of the axial flow fan 2 or beneath the motor, if the prior art axial flow fan shroud is adopted, products of high quality and high price having superior thermal properties must be used on the parts, and so, a high cost must be paid due to a rise of manufacturing prices.
Meanwhile, Japanese Patent Laid-open Publication No. 2005-61308 discloses a cooling device for a construction machine, which can uniformly distribute suction air to cores horizontally arranged in front of a cooling fan by horizontally expanding a suction area of air blowing by the cooling fan. In addition Japanese Utility Model Laid-open Publication No. 56-162469 discloses an axial flow fan shroud for a radiator, which has a distributing plate mounted at a position displaced outwardly from an axial direction of the axial flow fan in front of the axial flow fan for guiding an air flow toward the axial flow fan, so that the axial flow fan can suck and blow air through the radiator.
While such prior art shrouds enhance the cooling efficiency of the heat exchanger by uniformly distributing air sucked by the axial flow fan to the entire heat exchanger mounted in front of the axial flow fan, they do not change the flow direction of air blown toward the back of the axial flow fan. Therefore, in the case where the parts weak to heat due to the special restriction must be arranged at a position displaced from the axial direction of the axial flow fan in the downstream part of the axial flow fan, air blown by the axial flow fan cannot be induced toward the parts. Therefore, the prior has the above problems of the axial flow fan shroud.